Crude oil produced from geological formations contains various amounts of water. Water and crude oil are naturally non-miscible. When naturally occurring interfacial active compounds are present, however, these compounds can aggregate on the water and oil interface and cause oil droplets to disperse in the water phase. Such water external, oil internal two phase systems are commonly referred as reverse crude oil emulsions and can be quite stable. During crude oil lifting through production tubes, the water and oil encounters an increased mixing energy from rapid flow through chokes and bends. This additional mixing energy can further emulsify the water and oil. The presence of crude oil in water can interfere with water treatment and/or water re-injection systems. In particular, oil-free water is required for applications where water is discharged into the environment, such as overboard water on offshore platforms, or is used in steam generation, such as steam assisted gravity drainage.
Commonly used reverse emulsion-breaking chemicals, or water clarifiers, include the following: tridithiocarbamic acids (U.S. Pat. No. 5,152,927); dithiocarbamic salts (U.S. Pat. No. 5,247,087); dimethylaminoethyl acrylate methyl chloride and/or benzyl chloride quaternary salts (U.S. Pat. No. 5,643,460); polymeric quaternary ammonium betaines (U.S. Pat. No. 3,929,635); and metal salts (zinc chloride, aluminum chloride). Polymeric quaternary ammonium salts and copolymers of acrylic acid and acrylamide have also been used. These compounds, however, may not provide satisfactory performance in all instances. In particular, in extremely cold weather (e.g., −40° C. and below) various problems are known. These active ingredients are typically viscous and require a suitable solvent to reduce the viscosity of the reverse emulsion breaker blend.
A main challenge in oilfield production is the resolution of oil-in-water emulsions, otherwise known as reverse emulsions. Many reverse emulsion breakers also have a small window of treatment dosages, which makes it challenging and difficult to properly control resolution. Complex or multiple emulsions typically require both a reverse and a standard emulsion breaker to aid in its resolution into clean water and dry oil. These two products traditionally are incompatible, so each is typically injected separately.
There thus exists an ongoing need for new, economical and effective chemicals and processes for resolving reverse emulsions and complex emulsions into the component parts of water and oil.